Aspherical led lens and light emitting device including the same

ABSTRACT

An aspherical lens includes a light entrance plane configured to receive light emitted from a light source and a light exit plane configured to radiate the light received by the light entrance plane. The light exit plane includes semispherical convex portions disposed on an upper surface of the aspherical lens, a concavely depressed portion comprising an overlapping region where the semispherical convex portions partially overlap each other at a central axis, a side portion connected with the semispherical convex portions, and an upper surface of each of the semispherical convex portions having a first flat portion.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/081,338, filed on Nov. 15, 2013, which is a continuation of U.S.patent application Ser. No. 12/985,464, filed on Jan. 6, 2011, issued asU.S. Pat. No. 8,602,605, and claims priority from and the benefit ofKorean Patent Application No. 10-2010-0001059, filed on Jan. 7, 2010,and Korean Patent Application No. 10-2010-0028693, filed on Mar. 30,2010, which are hereby incorporated by reference for all purposes as iffully set forth herein.

BACKGROUND

1. Field

Exemplary embodiments of the present invention relate to a lens forlight emitting diodes (LEDs) and, more particularly, to an asphericalLED lens and a light emitting device is including the same.

2. Discussion of the Background

A LED refers to a semiconductor device that has a p-n junction and emitslight upon recombination of electrons and holes in the p-n junctionbased on a potential difference formed therein. An LED may be composedof compound semiconductors such as GaN, GaAs, GaP, GaAs_(1-x)P_(x),Ga_(1-x)Al_(x)As, InP, In_(1-x)Ga_(x)P, etc., and has generally beenused for display lamps or devices for displaying simple information suchas numerals. In recent years, with the development of technologies suchas information display technology and semiconductor technology, LEDs maybe used not only for flat panel displays such as liquid crystal displaydevices, but also for general lighting.

LEDs may have advantages, such as superior energy efficiency to andlonger lifespan than existing light sources, no discharge of harmfulultraviolet (UV) light, and environmental friendliness, and are thusincreasingly a focus of attention as a light source that can replaceexisting cold cathode fluorescent lamps (CCFL).

However, when LEDs are applied to a light source for a backlight unit ofa display device, a panel disposed directly on the LEDs may have highillumination but a region between the LEDs may have low illumination dueto point light source characteristics of the LEDs, whereby the entiretyof the panel may have uneven illumination. Further, when the LEDs areapplied to a street lamp, for example, only a region directly below thestreet lamp may be bright, and a road surface between street lamps maybe dark, causing pedestrian or driver inconvenience.

Specifically, a conventional LED will be described herein with referenceto an example wherein a semispherical LED lens is employed as a lightsource for a backlight unit.

FIG. 1 is a side sectional view of a light emitting device 100 includinga conventional semispherical LED lens, FIG. 2 is a graph depicting anorientation angle curve of light emitted from the light emitting device100, and FIG. 3 is a graph depicting illumination on a panel of adisplay device according to arrangement of the light emitting devices100 when the light emitting devices 100 are used as a light source forthe backlight unit.

As shown in FIG. 1, the conventional light emitting device 100 includesan LED chip 2 and a semispherical LED lens 4 which adjust an angle oflight emitted from the LED chip 2. Although not shown in the drawings,the light emitting device 100 may further include a fluorescent materialdeposited on the LED chip 2 to generate white light.

Referring to FIG. 2, since light emitted from the light emitting device100 as shown in FIG. 1 is focused on the center of the lens 4 due to thesemispherical structure of the lens 4, the light may have a symmetricalpattern of orientation angles such that illumination increases towards acentral axis of the lens and gradually decreases towards right and leftsides thereof.

Accordingly, as shown in FIG. 3, when the light emitting devices 100including the semispherical LED lenses are linearly arranged in thebacklight unit of the display device, illumination on a panel above thelight emitting devices 100 may be uneven, and bright and dark areas maybe repeatedly formed on the panel.

SUMMARY

Exemplary embodiments of the present invention provide an aspherical LEDlens and a light emitting device including the same, which may provide adouble peak type pattern of orientation angles of light emitted from anLED chip while minimizing chromatic aberration.

Exemplary embodiments of the present invention also provide anaspherical LED lens and a light emitting device including the same,which may make orientation angle curves of light emitted from a lightemitting diode chip asymmetrical with respect to a major axis and aminor axis of the LED lens.

Additional features of the invention will be set forth in thedescription which follows and in part will be apparent from thedescription, or may be learned by practice of the invention.

An exemplary embodiment of the present invention discloses an asphericallight emitting diode (LED) lens. The aspherical LED lens includes alight exit plane concavely depressed near a central axis, a lightentrance plane including a conical plane having a vertex located on thecentral axis, and a plurality of protrusions arranged on a portion of aside surface of the light exit plane, wherein the aspherical LED lenshas a radially symmetrical structure with respect to a central axisthereof.

An exemplary embodiment of the present invention also discloses a lightemitting device. The light emitting device includes a housing; a lightemitting diode (LED) chip arranged on the housing; and an aspherical LEDlens arranged on the LED chip, the aspherical LED lens having a radiallysymmetrical structure with respect to a central axis of the LED lens.The aspherical LED lens includes a light exit plane concavely depressednear the central axis; a light entrance plane including a conical planehaving a vertex located on the central axis, and a plurality ofprotrusions arranged on a portion of a side surface of the light exitplane.

An exemplary embodiment of the present invention also discloses a lightemitting device. The light emitting device includes a substrate, an LEDchip arranged on the substrate and an aspherical LED lens arranged onthe LED chip. The aspherical LED lens has different cross-sectionsrespectively taken along a major axis and a minor axis of the LED lens.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention, andtogether with the description serve to explain the principles of theinvention.

FIG. 1 is a side sectional view of a light emitting device including aconventional semispherical LED lens.

FIG. 2 is a graph depicting an orientation angle curve of light emittedfrom the light emitting device of FIG. 1.

FIG. 3 is a graph depicting illumination on a panel of a display devicewith an arrangement of the light emitting devices shown in FIG. 1.

FIG. 4 is a perspective view of a light emitting device including anaspherical LED lens.

FIG. 5 is a side sectional view of the light emitting device includingthe aspherical LED lens.

FIG. 6 is a graph depicting an orientation angle curve of light emittedfrom the aspherical LED lens.

FIG. 7 is a graph depicting chromatic aberration of the aspherical LEDlens.

FIG. 8 is a side sectional view of a light emitting device employing anaspherical LED lens including a plurality of side protrusions accordingto an exemplary embodiment of the present invention.

FIG. 9 is a graph depicting an orientation angle curve of light emittedfrom the aspherical LED lens of FIG. 8.

FIG. 10 is a graph depicting chromatic aberration of the aspherical LEDlens of FIG. 8.

FIGS. 11( a), 11(b) and 11(c) are side sectional views of aspherical LEDlenses including linear sections according to exemplary embodiments ofthe present invention.

FIGS. 12( a) and 12(b) are side sectional views of aspherical LEDlenses, each of which has a light exit plane composed of curved sectionshaving different radii of curvature, according to exemplary embodimentsof the present invention.

FIG. 13 is a perspective view of an aspherical LED lens according to anexemplary embodiment of the present invention.

FIG. 14 is a top view of the aspherical LED lens of FIG. 13.

FIG. 15 is a cross-sectional view of the aspherical LED lens of FIG. 13taken along a major axis of the lens.

FIG. 16 is a cross-sectional view of the aspherical LED lens of FIG. 13taken along a minor axis of the lens.

FIG. 17 is a graph depicting an orientation angle curve of a lightemitting device employing the aspherical LED lens of FIG. 13.

FIG. 18 is a cross-sectional view taken along a major axis of anaspherical LED lens according to an exemplary embodiment of the presentinvention.

FIG. 19 is a cross-sectional view of the aspherical LED lens of FIG. 18taken along a minor axis of the aspherical LED lens.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

The invention is described more fully hereinafter with reference to theaccompanying drawings, in which exemplary embodiments of the inventionare shown. This invention may, however, be embodied in many differentforms and should not be construed as limited to the exemplaryembodiments set forth herein. Rather, these exemplary embodiments areprovided so that this disclosure is thorough and will fully convey thescope of the invention to those skilled in the art. In the drawings, thesizes and relative sizes of layers and regions may be exaggerated forclarity. Like reference numerals in the drawings denote like elements.

It will be understood that when an element or layer is referred to asbeing “on” or “connected to” another element or layer, it can bedirectly on or directly connected to the other element or layer, orintervening elements or layers may be present. In contrast, when anelement is referred to as being “directly on” or “directly connected to”another element or layer, there are no intervening elements or layerspresent.

FIGS. 4 and 5 are a perspective view and a side sectional view of alight emitting device including an aspherical LED lens, and FIGS. 6 and7 are graphs depicting an orientation angle curve of light emitted fromthe aspherical LED lens of FIG. 4 and a graph depicting chromaticaberration of the aspherical LED lens of FIG. 4.

Referring to FIGS. 4 and 5, a light emitting device 200 includes ahousing 20 having a cavity 21 formed therein, an LED chip 12 mounted onthe housing 20, an encapsulation material 22 in the cavity 21, and anaspherical LED lens 14.

The aspherical LED lens 14 may be formed of a light-transmittingmaterial such as silicone, epoxy, glass or plastic and have phosphorsdispersed therein. Further, the aspherical LED lens 14 may include alight entrance plane 141 and a light exit plane 142, and has a radiallysymmetrical structure with respect to a central axis (y) of the LED lens14.

Here, the light entrance plane 141 refers to a plane, upon which lightemitted from the LED chip 12 and passing through the encapsulationmaterial 142 is incident, and is composed of a conical plane having avertex located on the central axis. An air layer 25 may be present in aspace between the light entrance plane 141 and the encapsulationmaterial 22. Further, the light exit plane 142 refers to a plane,through which light passing through the LED lens 14 is emitted to theoutside of the LED lens, and has an overlapped region of two convexsemispherical shapes partially overlapping each other around the centralaxis. The overlapped region around the central axis may be a concavelydepressed region.

With this configuration of the aspherical lens 14, the amount orintensity of light decreases near a center of the aspherical LED lens14, that is, near the central axis of the aspherical LED lens 14, andincreases near a periphery of the aspherical LED lens 14, therebyproviding an orientation angle curve as shown in FIG. 6. Specifically,when compared with FIG. 2, the orientation angle curve of FIG. 6 has twopeaks at both sides of the lens (near an angle of about +/−67 degrees)instead of the center of the lens (at an angle of zero), and the amountor intensity of light at the center of the graph is about 30˜40% of thepeak value.

Thus, when such an aspherical lens 14 is employed as a light source fora backlight unit of a display device, the display device may haveuniform illumination and brightness on the panel of the display devicethereby solving the problem of the conventional LED lens wherein brightareas are formed on regions of a panel directly above LED packages anddark areas are formed on regions of the panel between adjacent LEDpackages.

The aspherical lens 14, which does not include a dispersing agent, mayexhibit more severe chromatic aberration than the conventionalsemispherical lens 4 due to the shape of the lens, as in a chromaticaberration curve of FIG. 7. Specifically, in the orientation angle curveof the aspherical lens 14 not including a dispersing agent, anX-coordinate variation (ΔX) is about 0.047 and a Y-coordinate variation(ΔY) is about 0.082 at an orientation angle within ±90 degrees.Therefore, it can be seen that the aspherical lens 14 causes severechromatic aberration. As a result, spots such as yellow spots or yellowrings may be generated on the panel due to chromatic aberration.

On the other hand, when the aspherical lens 14 includes the dispersingagent to solve the problem of chromatic aberration, the dispersing agentmay undesirably reduce the amount of light emitted from the lens or mayhave an undesirable effect on the orientation angle. Therefore, the useof only the dispersing agent may be insufficient to achieve a reductionin the chromatic aberration.

Next, an aspherical lens according to one exemplary embodiment will bedescribed with reference to FIGS. 8 to 10.

FIG. 8 is a side sectional view of a light emitting device having anaspherical LED lens including a plurality of side protrusions accordingto an exemplary embodiment of the present invention. FIGS. 9 and 10 arean orientation angle curve of light emitted from the aspherical LED lensof FIG. 8 and a chromatic aberration graph of the aspherical LED lens,respectively.

Referring to FIG. 8, a light emitting device 1000 includes a housing 320having a cavity 321 formed therein, an LED chip 322, an encapsulationmaterial 323 and an aspherical LED lens 360.

In the housing 320, the cavity 321 has a predetermined depth and may beconfigured to surround the LED chip 322. Advantageously, the depth ofthe cavity 321 may be greater than or equal to the height of the LEDchip 322.

The encapsulation material 323 is a light-transmitting material, such assilicone or epoxy, with which the cavity 321 is filled, and encapsulatesthe LED chip 322 to cover and protect the LED chip 322.

The LED chip 322 is mounted on an upper surface of the housing 320 andemits, for example, blue light in a wavelength band of 430˜480 nm or UVlight in a wavelength band of 350˜410 nm. Alternatively, the LED chip322 may be configured to emit other colors. As such, the presentinvention is not limited to a specific LED chip.

The LED chip 322 is mounted on the upper surface of the housing 320 andmay be placed at a location where a central axis of the aspherical LEDlens 360 meets the housing 320. Specifically, the LED chip 322 may bedisposed at the center of the aspherical LED lens 360, which may bebonded or joined to the upper surface of the housing 320 including theLED chip 322 by an adhesive or other means. Although the aspherical LEDlens 360 is illustrated as being disposed over a single LED chip in FIG.8, it should be understood that the aspherical LED lens may be disposedover a plurality of LED chips. That is, the plural LED chips may bedisposed at the central axis (or at the center) of the LED lens 360 andaround the central axis thereof.

Further, a fluorescent material may be directly deposited on the LEDchip 322 or contained in the encapsulation material 323 or a resinconstituting the aspherical LED lens 360. Here, the fluorescent materialmay emit light of a certain color using light emitted from the LED chip322 as an excitation source. For example, if the LED chip 322 is a blueLED chip composed of semiconductors for emitting light in a wavelengthband of 430˜480 nm, phosphors emitting yellow-green or yellow lightusing some of the light as an excitation source are deposited on the LEDchip 322, so that the light emitting device can emit white light by acombination of blue light emitted from the LED chip 322 and yellow-greenor yellow light emitted from the phosphors.

Further, the aspherical LED lens 360 includes a light entrance plane 361and a light exit plane 362, and has a radially symmetrical structurewith respect to a central axis (y) of the LED lens 360.

Here, the light entrance plane 361 refers to a plane, upon which lightemitted from the LED chip 322 and passing through the encapsulationmaterial 323 is incident, and is composed of a conical plane having avertex located on the central axis (y). An air layer 324 may be presentin a space between the light entrance plane 361 and the encapsulationmaterial 323. Further, the light exit plane 362 refers to a plane,through which light passing through the lens 360 is emitted to theoutside of the LED lens 360, and has an overlapped region of two convexsemispherical shapes C1, C2 partially overlapping each other around thecentral axis (y). The overlapped region around the central axis (y) maybe a concavely depressed region. Further, the light exit plane 361includes a plurality of protrusions (roughness) 363 partially formed ona side surface thereof. As shown in FIG. 8, the protrusions 363 may beformed over a region from a point below the highest point of the lightexit plane, for example, from a point corresponding to about ¼˜⅓ of theoverall lens width from either end of the lens, to the end of the lens.The protrusions 363 may be formed on the side surface of the light exitplane by forming protrusions (roughness) of about 0.4˜1.0 μm height fromthe LED lens 360 surface on a mold through sand blasting, followed byinjection molding a liquid silicone rubber described below into themold.

Different from the conventional semispherical lens 4, the asphericallens 360 exhibits a decrease in amount or intensity of light near thecenter of the lens (near the central axis) and exhibits an increase inamount or intensity of light near the periphery of the lens, therebyproviding an orientation angle curve of light as shown in FIG. 9.

Specifically, the orientation angle curve of FIG. 9 has two peaks atboth sides of the lens (near an angle of about +/−67 degrees) instead ofthe center of the lens (at an angle of zero), an angle between the twopeaks, that is, a peak-to-peak angle, is about 110 degrees, and theamount or intensity of light at the center of the graph is about 30˜40%,more accurately, about 36%, of the peak value. Namely, the formation ofthe side protrusions 363 does not change an original orientation anglecurve, unlike the case where the reduction of chromatic aberration isattempted using the dispersing agent.

Next, referring to FIG. 10, chromatic aberration of the aspherical LEDlens 360 of FIG. 8 is illustrated. Specifically, in the orientationangle curve of the aspherical LED lens 360, X-coordinate variation (ΔX)is about 0.028 and Y-coordinate variation (ΔY) is 0.049 at anorientation angle within ±90 degrees. Accordingly, the aspherical LEDlens 360 has reduced chromatic aberration through significant reductionof the X-coordinate variation (ΔX) and the Y-coordinate variation (ΔY),as compared with the chromatic aberration graph (ΔX=about 0.047,ΔY=0.082) of FIG. 7.

Consequently, when the aspherical lens 360 including the sideprotrusions 363 is employed as a light source for a backlight unit of adisplay device, for example, the display device has uniform illuminationand brightness on the panel of the display device while eliminatingspots such as yellow spots or yellow rings caused by the chromaticaberration. In addition, as the chromatic aberration is reduced by theformation of the side protrusions 363 without using the dispersingagent, the display device does not suffer deterioration in brightnesscaused by a reduction in the amount of light passing through the lens.

In fabrication of the aspherical LED lens 360 according to the presentexemplary embodiment, a light-transmitting material such as silicone,epoxy, glass or plastic may be used. For example, liquid silicone rubber(LSR) has sufficiently low viscosity to provide good flexibility andsuffers less decrease in viscosity at high temperature than currentlyused adhesive silicone resins, thereby providing improved workability.In addition, the LSR permits automatic production by injection moldingdue to low viscosity thereof and provides excellent productivity.Furthermore, since the LSR does not exhibit release properties withrespect to a mold, the LSR may not cause a lens interface phenomenon andpermits easy formation of the protrusions (roughness) on the lens whenforming the protrusions by sand blasting on the surface of the mold.

According to an exemplary embodiment, the dispersing agent is mixed witha silicone resin used in fabrication of the aspherical LED lens 360 toachieve a further reduction of chromatic aberration. For example, anaspherical LED lens may be produced by injection molding of a mixtureprepared by mixing the LSR with a SiO₂ dispersing agent. In this case,since the dispersing agent may reduce the amount of light in proportionto reduction in the degree of chromatic aberration or provide adifferent orientation angle curve from that shown in FIG. 9, the mixingratio of the dispersing agent in the LSR may be adjusted accordingly.

Experiments showed that the aspherical LED lens exhibited desiredbrightness with less chromatic aberration when the dispersing agent ismixed in an amount of about 0.3˜0.4% with respect to the total amount ofthe LSR. The present invention is not limited to a specific kind ormixing ratio of dispersing agent.

FIGS. 11( a), 11(b) and 11(c) are side sectional views of aspherical LEDlenses including linear sections according to exemplary embodiments ofthe present invention, respectively. A repeated description of elementsdescribed above will be omitted herein for clarity.

Referring to FIG. 11( a), a light exit plane may include linearsections. Specifically, the light exit plane of an aspherical LED lens400 a includes linear sections 420 near a concavely depressed portion, aside section 440 including a curved surface, and a linear section 430disposed between the linear section and the side section. In analternative embodiment, as shown in FIG. 11( c), a light exit plane ofan aspherical lens 400 c may include linear sections 420 only near thedepressed portion without the linear section 430. Namely, each of thelight exit planes of the aspherical LED lenses according to theseembodiments may include at least two linear sections 420 that meet atthe central axis (y) of the lens.

Further, the aspherical LED lens 400 a of FIG. 11( a) has the linearsections 420 slanted at about 18 degrees with respect to the horizontal,an aspherical LED lens 400 b of FIG. 11( b) has linear sections 420slanted at about 30 degrees with respect to the horizontal, and theaspherical lens 400 c of FIG. 11( c) has linear sections 420 slanted atabout 40 degrees with respect to the horizontal.

For the respective aspherical lenses of FIGS. 11( a) to 11(c), thedegree of chromatic aberration and generation of yellow spots on thepanel are listed in the following Table 1.

TABLE 1 Chromatic aberration Yellow spot (orientation angle ±90°) onpanel Lens 400a Δx = 0.021/Δy = 0.069 No occurrence Lens 400b Δx =0.016/Δy = 0.038 No occurrence Lens 400c Δx = 0.032/Δy = 0.072Occurrence

For the degree of chromatic aberration, the X-coordinate variation (ΔX)and the Y-coordinate variation at an orientation angle within ±90degrees are Δx=0.021/Δy=0.069 for the lens 400 a, Δx=0.016/Δy=0.038 forthe lens 400 b, and Δx=0.032/Δy=0.072 for the lens 400 c. The lens 400 cgenerates yellows spots on the panel due to the chromatic aberration,unlike the lenses 400 a, 400 b.

Consequently, for the light exit plane of the aspherical lens 400including at least two linear sections 420 that meet each other at thecentral axis, chromatic aberration is pronounced when each of the linearsections is slanted at an angle of about 35˜40 degrees or more withrespect to the horizontal direction.

Accordingly, when producing the aspherical lens including the linearsections according to the present exemplary embodiment, the inclinationof the linear sections may be adjusted to about 10˜40 degrees withrespect to the horizontal direction by taking into consideration thatsevere chromatic aberration may occur depending on the inclination ofthe linear sections near the depressed portion of the aspherical lens atan angle greater than about 35-40 degrees.

Meanwhile, although roughness or protrusions are not shown on a sidesurface 440 of each of the aspherical lenses in FIGS. 11( a), 11(b) and11(c) for clarity of illustration, each of the light exit planes mayfurther include the roughness or protrusion on the side surface thereofto reduce chromatic aberration.

FIGS. 12( a) and 12(b) are side sectional views of aspherical LEDlenses, each of which has a light exit plane composed of curved sectionshaving different radii of curvature, according to exemplary embodiments.A repeated description of elements described above will be omittedherein for clarity.

Referring to FIGS. 12( a) and 12(b), a light exit plane 520 of anaspherical LED lens 500 is not composed of a single curved sectionhaving a single radius of curvature. Instead, the light exit plane 520may be composed of plural curved sections having different radii ofcurvature. Namely, the light exit plane 520 may be composed of acombination of the curved sections having different radii of curvature.Specifically, in FIG. 12( a), the light exit plane 520 is composed ofcurved sections having a radius of curvature of R1=1.39 and a radius ofcurvature of R2=1.46, respectively, and in FIG. 12( b), the light exitplane 520 is composed of curved sections having a radius of curvature ofR1=0.5 and a radius of curvature of R2=1.054, respectively.

In other words, the light exit plane 520 of FIG. 12( a) is generallycomposed of the curved sections having relatively large radii ofcurvature (that is, small curvatures), and the light exit plane 520 ofFIG. 12( b) is generally composed of the curved sections havingrelatively small radii of curvature (that is, large curvatures). For therespective aspherical lenses of FIGS. 12( a) and 12(b), the degree ofchromatic aberration and generation of yellow spots on the panel arelisted in the following Table 2.

TABLE 2 Chromatic aberration Yellow spot (orientation angle ±90°) onpanel Lens 500a  Δx = 0.04/Δy = 0.072 No occurrence Lens 500b Δx =0.072/Δy = 0.109 Occurrence

For the degree of chromatic aberration, the X-coordinate variation (ΔX)and the Y-coordinate variation (ΔY) at an orientation angle within ±90degrees are Δx=0.04/Δy=0.072 for the lens 500 a having the light exitplane 520 generally composed of the curved sections having large radiiof curvature, and are Δx=0.072/Δy=0.109 for the lens 500 b having thelight exit plane 520 generally composed of the curved sections havingsmall radii of curvature. The lens 500 b generates yellow spots oryellow rings on the panel due to the chromatic aberration, unlike thelens 500 a.

Consequently, in the formation of the aspherical lens 500, chromaticaberration is severe at some regions of the light exit plane havingsmall radii of curvature.

Accordingly, when producing the aspherical lens including the pluralcurved sections having different radii of curvature, it is desirable toadjust the radii of curvature of the curved sections to about 1.0˜5.0 bytaking into consideration that severe chromatic aberration can occur atregions of the light exit plane having a radii of curvature less thanabout 1.3.

Meanwhile, although roughness or protrusions are not shown on a sidesurface of the light exit plane in FIGS. 12( a) and 12(b) for clarity ofillustration, each of the aspherical lenses may further include theroughness or protrusion on the side surface of the light exit plane toreduce chromatic aberration.

Next, an aspherical LED lens 2200 according to an exemplary embodimentof the present invention will be described with reference to FIGS. 13and 14. FIG. 13 is a perspective view of an aspherical LED lensaccording to the exemplary embodiment and FIG. 14 is a top view of theaspherical LED lens of FIG. 13.

Referring to FIG. 13, the aspherical LED lens 2200 of the presentexemplary embodiment includes a first lens section 2210, a second lenssection 2220, and a supporting section 2230. The first and second lenssections 2210, 2220 (also referred to as a “lens part”) are symmetricalwith respect to the central axis Y. The lens sections have substantiallysemispherical shapes and are in surface contact with each other suchthat the overall shape of the aspherical LED lens 2200 except for thesupporting section 2230 is similar to a peanut shape when view fromabove, as shown in FIG. 14.

Specifically, referring to FIG. 14, the lens part of the aspherical LEDlens 2200 according to the present exemplary embodiment has a shape inwhich two semispherical convex lenses indicated by a dotted line are insurface contact with each other, with side surfaces 2340, 2340′, 2440,2440′ of the lens shifted inwards from the circular dotted line in adirection indicated by arrows. In this manner, as the first and secondlens sections 2210, 2220 are in surface contact with each other to forman elongated lens part having a peanut shape, the orientation anglecurve of the aspherical LED lens 2200 is different from that of theconventional LED lens 4 shown in FIG. 1. Further, it is possible toadjust a lateral width of an area illuminated by the light emittingdevice by adjusting a distance by which the side surfaces 2340, 2340′,2440, 2440′ of the lens are shifted. In other words, as the sidesurfaces 2340, 2340′, 2440, 2440′ of the lens are shifted inwards toreduce the thickness of the aspherical LED lens 2200, the width of theilluminated area may be narrowed.

The supporting section 2230 is not limited to a specific structure. Forexample, the supporting section 2230 may be integrally formed with thefirst and second lens sections 2210, 2220. Alternatively, the supportingsection 2230 may be separately prepared and attached to the first andsecond lens sections 2210, 2220. The supporting section 2230 covers thesubstrate 2240 having an LED chip 2120 (see FIG. 15) mounted thereon soas to cover not only the LED chip 2120, but also a bonding wire (notshown) electrically connected to an electrode formed on the LED chip2120 and a patterned electrode (not shown) formed on the substrate 2240to supply power to the LED chip 2120, so that these elements may beprevented from being exposed to air and can be protected from externalimpact or moisture.

Details of the lens part of the aspherical LED lens 2200 according tothe present exemplary embodiment will be described in more detail withreference to FIGS. 15 and 16, which illustrate an LED package, that is,a light emitting device, including the aspherical LED lens 2200.

FIG. 15 is a cross-sectional view of a light emitting device 2000including the aspherical LED lens 2200 of FIG. 13 taken along a majoraxis of the lens, that is, along line A-A′ of FIG. 13. FIG. 16 is across-sectional view of the light emitting device 2000 including theaspherical LED lens 2200 of FIG. 13 taken along a minor axis of thelens, that is, along line B-B of FIG. 13. It should be noted that FIGS.15 and 16 illustrate characteristic features of the invention withoutillustration of elements, such as a lead frame, an electric circuit, anelectric wire, and the like, which are used for operation or otherfunctions of the light emitting device 2000 but are not directly relatedto the scope of the invention, for clarity of illustration.

As shown in FIGS. 15 and 16, the light emitting device 2000 according tothe present exemplary embodiment may include a substrate 2240, an LEDchip 2120 mounted on the substrate 2240, and an aspherical LED lens2200.

Any substrate may be used as the substrate so long as the substrateallows a high density of LED chips 2120 to be mounted thereon. Examplesof such a substrate include, but are not limited to, alumina, quartz,calcium zirconate, forsterite, SiC, graphite, fused silica, mullite,cordierite, zirconia, beryllia, aluminum nitride, and low temperatureco-fired ceramic (LTCC). The ceramic material may be applied to amulti-layer ceramic package (MLP), which includes a pattern of metallicconductor wires formed thereon and subjected to sintering. The ceramicmaterial used for such a semiconductor package provides excellentair-tightness.

Further, although not shown in the drawings, the substrate 2240 haspatterned electrodes, which are formed of a highly conductive metal suchas copper or aluminum and may be separately formed corresponding to ananode and a cathode of the LED chip 2120.

The LED chip 2120 may be, for example, a blue LED chip that emits bluelight in a wavelength band of 430˜480 nm or a UV LED that emits UV lightin a wavelength band of 350˜410 nm. Alternatively, the LED chip 2120 maybe configured to emit other colors. As such, the present invention isnot limited to a specific LED chip.

The LED chip 2120 is mounted on an upper surface of the substrate 2240and may be placed at a location where the central axis of the asphericalLED lens 2200 meets the substrate 2240. Specifically, the LED chip 2120may be disposed at the center of the aspherical LED lens 2200, which maybe bonded or joined to the upper surface of the substrate 2240 includingthe LED chip 2120 by an adhesive or other means. Although the asphericalLED lens 2200 is illustrated as including a single LED chip in FIGS. 15and 16, the aspherical LED lens may include a plurality of LED chips.

Further, although not shown in the drawings, a fluorescent material maybe directly deposited on the LED chip 2120 to generate a certain colorusing light emitted from the LED chip 2120 as an excitation source. Forexample, if the LED chip 2120 is a blue LED chip composed ofsemiconductors for emitting light in a wavelength band of 430˜480 nm,phosphors emitting yellow-green or yellow light using some of the lightas an excitation source are deposited on the LED chip 2120, so that thelight emitting device can emit white light by a combination of bluelight emitted from the LED chip 2120 and yellow-green or yellow lightemitted from the phosphors. Further, the fluorescent material may bedirectly deposited on the LED chip 2120 or may be contained in a resinfor forming the aspherical LED lens 2200. Alternatively, the fluorescentmaterial may be provided as a separate phosphor sheet.

The aspherical LED lens 2200 serves to adjust an orientation angle oflight by changing a travel direction of light emitted from the LED chip2120 and may be formed of a light-transmitting material such assilicone, epoxy, glass or plastic.

According to the present exemplary embodiment, the aspherical LED lens2200 includes a first lens section 2210 and a second lens section 2220positioned symmetrically about the central axis Y and a supportingsection 2230 formed under the first and second lens sections 2210, 2220.In other words, the first and second lens sections 2210, 2220 are insurface contact with each other to form a convexly protruded shape at acentral region 2510 of the lens, as shown in FIG. 16.

Referring again to FIG. 15, on the cross-section of the aspherical LEDlens 2200 taken along the major axis of the LED lens, the first andsecond lens sections 2210, 2220 are bilaterally symmetrical.Specifically, the first lens section 2210 includes a first slantedportion 2310, a first flat portion 2320 and a first convex portion 2330,and the second lens section 2220 includes a second slanted portion 2410,a second flat portion 2420 and a second convex portion 2430. Thus, thefirst slanted portion 2310, the first flat portion 2320 and the firstconvex portion 2330 may be symmetrical to and have the same length asthe second slanted portion 2410, the second flat portion 2420, and thesecond convex portion 2430, respectively.

Specifically, the first flat portion 2320 and the second flat portion2420 are the uppermost flat regions of the first lens section 2210 andthe second lens section 2220 (see FIG. 14) to form linear structures,respectively. Each of the first slanted portion 2310 and the secondslanted portion 2410 is connected to one end of each of the first flatportion 2320 and the second flat portion 2420, and may be a curvedsurface slanted towards the central axis Y. Thus, the first slantedportion 2310 and the second slanted portion 2410 are coupled to eachother at the central axis Y to form a concave cross-section at thecenter of the aspherical LED lens 2200. Further, each of the firstconvex portion 2330 and the second convex portion 2430 is connected tothe other end of each of the first flat portion 2320 and the second flatportion 2420, and is a curved surface bulging towards an outside of theaspherical LED lens 2200. Here, the first slanted portion 2310 (or thesecond slanted portion 2410) may have the same or different curvaturefrom the first convex portion 2330 (or the second convex portion 2430).

When emitted from the LED chip 2120 to the outside, light is refractedaway from the central axis Y by a difference in refractive index betweenair and the resin for forming the aspherical LED lens 2200 and angles ofslanted outer surfaces of the first and second lens sections 2210, 2220.FIG. 15 schematically illustrates an optical path of light emitted fromthe LED chip 2120 using an arrow. Further, a light orientation anglecurve of the aspherical LED lens 2200 is shown in FIG. 17. The lightorientation angle curve of the aspherical LED lens 2200 will bedescribed below.

Referring to FIG. 16, the cross-section of the aspherical LED lens 2200taken along line B-B of FIG. 13 is shown.

The minor axis cross-section of the aspherical LED lens 2200 may includea central lens region 2510, first and second planes 2520, 2530respectively connected to both ends of the central lens region 2510, anda supporting section 2230. As can be seen from FIG. 16, the minor axiscross-section of the aspherical LED lens 2200 substantially has a “

” shape with the central lens region 2510 convexly protruded, and isdifferent from the major axis cross-section of the aspherical LED lens2200 shown in FIG. 15.

As in FIG. 15, FIG. 16 schematically illustrates an optical path oflight emitted from the LED chip 2120 using an arrow. Unlike the opticalpath of FIG. 15, when emitted from the LED chip 2120, light is refractedtowards the central axis of the LED lens 2200 on the first and secondplanes 2520, 2530 of the aspherical LED lens 2200 such that severallight beams can be directed upwards outside the aspherical LED lens2200.

Next, referring to FIG. 17, the light orientation angle curve of thelight emitting device 2000, as a product of the aspherical LED lens 2200according to the present exemplary embodiment, will be described. InFIG. 17, a dashed line indicates a light orientation angle curve on themajor axis cross-section of the lens and a solid line indicates a lightorientation angle curve on the minor axis cross-section of the lens.

Referring to FIG. 17, when using the aspherical LED lens 2200, the lightorientation angle curve on the major axis cross-section of the LED lens2200 generally has an M-shaped curve due to a relative decrease inoptical intensity at the center of the lens 2200 and a significantincrease in optical intensity at both sides of the lens 2200. On thecontrary, in the light orientation angle curve on the minor axiscross-section of the LED lens 2200, optical intensity relativelyincreases at the center of the aspherical LED lens 2200 and graduallydeceases towards both sides of the aspherical LED lens 2200, since thelight is focused on the center of the lens.

In other words, the light orientation angle curve on the major axiscross-section of the aspherical LED lens 2200 is different from thelight orientation angle curve on the minor axis cross-section of theaspherical LED lens 2200, thereby forming asymmetrical light orientationangle curves.

Particularly, in the orientation angle curve on the major axiscross-section of the LED lens 2200 shown in FIG. 13, peak angles at bothsides of the lens are about 50˜70 degrees and the intensity of light atthe center of the lens is about 40˜50% of the peak value. On thecontrary, in the orientation angle curve on the minor axis cross-sectionof the LED lens 2200, the orientation angle is about 70˜90 degrees.

Thus, when the light emitting device 2000 employs the aspherical LEDlens 2200, light is broadly emitted from right and lefts sides of thelight emitting device 2000 with reference to a major axis plane of theaspherical LED lens 2200. Accordingly, when such light emitting devices2000 are used for a street lamp, for example, it is possible to form anelongated illumination area along a roadside using light emitted fromthe light emitting devices 2000. Further, since light is focused on thecenter of the lens with reference to a minor axis plane of theaspherical LED lens 2200, a road area within a certain radius of thestreet lamp can be illuminated with higher brightness than other areas.In other words, the light emitting device 2000 including the asphericalLED lens 2200 emits light in different patterns along the major axis andthe minor axis of the aspherical LED lens, thereby making it possible toachieve efficient illumination of a road according to a road conditionwhen applied to the street lamp.

FIGS. 18 and 19 illustrate a light emitting device 3000 including anaspherical LED lens 3200 according to an exemplary embodiment of thepresent invention. Specifically, FIG. 18 is a cross-sectional view ofthe light emitting device 3000 taken along a major axis of theaspherical LED lens 3200 and FIG. 19 is a cross-sectional view of thelight emitting device 3000 taken along a minor axis of the asphericalLED lens 3200. It should be noted that FIGS. 18 and 19 illustratecharacteristic features of the invention without illustration ofelements, such as a lead frame, an electric circuit, an electric wire,and the like, which are used for operation or other functions of thelight emitting device 3000 but are not directly related to the scope ofthe invention, for clarity of illustration. A repeated description ofelements described in FIGS. 15 and 16 will be omitted herein.

As shown in FIGS. 18 and 19, the light emitting device 3000 according tothe present exemplary embodiment may include a substrate 3240, an LEDchip 3120 mounted on the substrate 3240, and the aspherical LED lens3200.

Unlike the light emitting device 2000 shown in FIGS. 15 and 16, thesubstrate 3240 may include a cavity depressed to a predetermined depth.Accordingly, as described below, although the aspherical LED lens 3200does not include the supporting section, the LED chip 3120 can beprotected by the aspherical LED lens 3200, since the LED chip 3120 ismounted in the cavity.

The LED chip 3120 may be, for example, a blue light emitting diode chipthat emits blue light in a wavelength band of 430˜480 nm or a UV lightemitting diode chip that emits UV light in a wavelength band of 350˜410nm. Alternatively, the LED chip 3120 may be configured to emit othercolors of light. As such, the present invention is not limited to aspecific LED chip.

The LED chip 3120 is mounted in the cavity on the substrate 3240 and maybe placed at a location where a central axis of the aspherical LED lens3200 meets the substrate 3240. Specifically, the LED chip 3120 may bedisposed at the center of the aspherical LED lens 3200, which may bebonded or joined to the upper surface of the substrate 3240 includingthe LED chip 3120 by an adhesive or other means. Although the asphericalLED lens 3200 is illustrated as including a single LED chip 3120 inFIGS. 18 and 19, it should be understood that the aspherical LED lensmay include a plurality of LED chips.

Further, although not shown in the drawings, a fluorescent material maybe directly deposited on the LED chip 3120 to generate a certain colorusing light emitted from the LED chip 3120 as an excitation source.Here, the fluorescent material may be contained in a resin for formingthe aspherical LED lens 3200. Alternatively, the fluorescent materialmay be provided as a separate phosphor sheet.

The aspherical LED lens 3200 serves to adjust an orientation angle oflight by changing a travel direction of light emitted from the LED chip3120 and may be formed of a light-transmitting material such assilicone, epoxy, glass or plastic.

According to the present exemplary embodiment, the aspherical LED lens3200 includes a first lens section 3211 and a second lens section 3221positioned symmetrically about the central axis Y, without thesupporting section as described above. The first and second lenssections 3211, 3221 are in surface contact with each other to form aconvexly protruded shape at a central region 3511 of the lens, as shownin FIG. 19.

Referring again to FIG. 18, on a major axis cross-section of theaspherical LED lens 3200, the first and second lens sections 3211, 3221are bilaterally symmetrical. Specifically, the first lens section 3211includes a first slanted portion 3311, a first flat portion 3321 and afirst convex portion 3331, and the second lens section 3211 includes asecond slanted portion 3411, a second flat portion 3421 and a secondconvex portion 3431. Thus, the first slanted portion 3311, the firstflat portion 3321 and the first convex portion 3331 may be symmetricalto the second slanted portion 3411, the second flat portion 3421, andthe second convex portion 3431, respectively. In particular, since thefirst slanted portion 3311 and the first convex portion 3331 aresymmetrical to the second slanted portion 3411 and the second convexportion 3431, respectively, the first slanted portion 3311 and the firstconvex portion 3331 may have the same lengths and radii of curvature asthose of the second slanted portion 3411 and the second convex portion3431, respectively.

Specifically, the first flat portion 3321 and the second flat portion3421 are the uppermost flat regions of the first lens section 3211 andthe second lens section 3221 to form linear structures, respectively.Each of the first slanted portion 3311 and the second slanted portion3411 is connected to one end of each of the first flat portion 3321 andthe second flat portion 3421, and may be a curved surface slantedtowards the central axis Y. Thus, the first slanted portion 3311 and thesecond slanted portion 3411 are coupled to each other at the centralaxis Y to form a concave cross-section at the center of the asphericalLED lens 3200. Further, each of the first convex portion 3331 and thesecond convex portion 3431 is connected to the other end of each of thefirst flat portion 3321 and the second flat portion 3421, and is acurved surface bulging towards an outside of the aspherical LED lens3200. Here, the first slanted portion 3311 (or the second slantedportion 3411) may have the same or different curvature from the firstconvex portion 3330 (or the second convex portion 3430).

When emitted from the LED chip 3120 to the outside, light is refractedaway from the central axis Y by a difference in refractive index betweenair and the resin for forming the aspherical LED lens 3200 and angles ofslanted outer surfaces of the first and second lens sections 3210, 3220.

Referring now to FIG. 19, the minor axis cross-section of the asphericalLED lens 3200 may include a central lens region 3511 and first andsecond planes 3521, 3531 respectively connected to both ends of thecentral lens region 2510, and need not include the supporting section.When emitted from the LED chip 3120, light is refracted towards thecentral axis of the lens on the first and second planes 3521, 3531 ofthe aspherical LED lens 3200 such that several light beams can bedirected upwards outside the aspherical LED lens 3200.

Therefore, the orientation angle curve of the aspherical LED lens 3200has the shape of FIG. 17, which is similar to the shape of theorientation angle curve of the aspherical LED lens described above.Specifically, when using the aspherical LED lens 3200, the lightorientation angle curve on the major axis cross-section of theaspherical LED lens 3200 generally has an M-shaped curve due to arelative decrease in optical intensity at the center of the asphericalLED lens 3200 and a significant increase in optical intensity at bothsides of the aspherical LED lens 3200. On the contrary, in the lightorientation angle curve on the minor axis cross-section of theaspherical LED lens 3200, the optical intensity relatively increases atthe center of the aspherical LED lens 3200 and gradually deceasestowards both sides of the aspherical LED lens 3200, since the light isfocused on the center of the lens. As such, the light orientation anglecurve on the major axis cross-section of the aspherical LED lens 3200 isdifferent from the light orientation angle curve on the minor axiscross-section of the aspherical LED lens 3200, thereby formingasymmetrical light orientation angle curves.

Particularly, in the orientation angle curve on the major axiscross-section of the LED lens 3200, peak angles at both sides of thelens are about 50˜70 degrees and the intensity of light at the center ofthe lens is about 40˜50% of the peak value. On the contrary, in theorientation angle curve on the minor axis cross-section of the LED lens3200, the orientation angle is about 70˜90 degrees.

Thus, when the light emitting device 3000 employing the aspherical LEDlens 3200 is used for a street light, for example, it is possible toform an elongated illumination area along a roadside using light emittedfrom the light emitting devices 3000. Further, since light is focused onthe center of the lens with reference to a minor axis plane of theaspherical LED lens 3200, a road area within a certain radius of thestreet lamp can be illuminated with higher brightness than other areas.

The aspherical LED lens according to exemplary embodiments of thepresent invention may be used to provide a double-peak orientation anglecurve of light. Accordingly, a display device employing the asphericalLED lens as a light source for a backlight unit can provide uniformillumination to a panel of the display device while significantlyreducing chromatic aberration.

In addition, when a light emitting device employing the aspherical LEDlens is used for a display device, the display device has uniformillumination or brightness on the panel of the display device andeliminates spots caused by chromatic aberration, thereby improvingdisplay quality.

According to other exemplary embodiments of the present invention, theorientation angle curve on the major axis of the aspherical LED lens haspeak angles at locations deviated from the center of the LED lens andthe orientation angle curve on the minor axis of the aspherical LED lenshas a peak angle at the center of the LED lens, so that he asphericalLED lens provides different light orientation angle curves in thedirections of the major axis and the minor axis of the LED lens.

Accordingly, when light emitting devices employing such an asphericalLED lens are used for street lights, the light emitting devices mayprovide an illumination region longitudinally formed along a roadside.

Although the invention has been illustrated with reference to someexemplary embodiments in conjunction with the drawings, it will beapparent to those skilled in the art that various modifications andchanges can be made to the invention without departing from the spiritand scope of the invention. Therefore, it should be understood that theembodiments are provided by way of illustration only and are given toprovide complete disclosure of the invention and to provide thoroughunderstanding of the invention to those skilled in the art. Thus, it isintended that the invention covers the modifications and variations ofthis invention provided they come within the scope of the appendedclaims and their equivalents.

What is claimed is:
 1. An aspherical lens, comprising: a light entranceplane configured to receive light emitted from a light source; and alight exit plane configured to radiate the light received by the lightentrance plane, wherein the light exit plane comprises: semisphericalconvex portions disposed on an upper surface of the aspherical lens; aconcavely depressed portion comprising an overlapping region where thesemispherical convex portions partially overlap each other at a centralaxis, a side portion connected with the semispherical convex portions;and an upper surface of each of the semispherical convex portionscomprises a first flat portion.
 2. The aspherical lens of claim 1,wherein the side portion comprises a curved surface.
 3. The asphericallens of claim 1, wherein the concavely depressed portion comprises acurved surface.
 4. The aspherical lens of claim 1, wherein the firstflat portion is disposed between the overlapping region and the sideportion.
 5. The aspherical lens of claim 1, wherein: the concavelydepressed portion and the side portion each comprise curved surfaces;and the first flat portion is disposed between the curved surface of theconcavely depressed portion and the curved surface of the side portion.6. The aspherical lens of claim 1, wherein the first flat portion isperpendicular to the central axis.
 7. The aspherical lens of claim 1,wherein at least one surface of the light entrance plane comprises asecond flat portion.
 8. The aspherical lens of claim 7, wherein animaginary line parallel to the central axis intersects the first flatportion and the second flat portion.
 9. The aspherical lens of claim 7,wherein an imaginary line parallel to the central axis intersects afirst part of the second flat portion and the light source, such thatthe first part overlaps the light source.
 10. The aspherical lens ofclaim 1, wherein the first flat portion surrounds the concavelydepressed portion in a circular shape.
 11. An aspherical lens,comprising: a light entrance plane configured to receive light emittedfrom a light source; and a light exit plane configured to radiate thelight received by the light entrance plane, wherein the light exit planecomprises: a concavely depressed portion disposed along a central axis;a semispherical convex portion surrounding the concavely depressedportion; and a side portion connected with the semispherical convexportion, wherein: an upper surface of the semispherical convex portioncomprises a first flat portion; and the light entrance plane comprises asecond flat portion.
 12. The aspherical lens of claim 11, wherein animaginary line parallel to the central axis intersects the first flatportion and the second flat portion.